Scientist? Banker? My Little Pony fanatic?

Anna the scientist came dressed as a pony. With rainbow hair, a bright yellow body and little green birds on her rump, obviously. "And wings. I'm Sky Dancer."

Right. Don't panic. Sky Dancer is the name of a toy. One of the original Pegasus horses in the My Little Pony range that came out in the early Eighties. If you knew that, you should have been at PonyCon yesterday.

You could have bought a rare Minty. You could have gasped at customised Goth ponies in black fishnets. You could have dressed up like Anna or Lorna, the woman from the Home Office in a bright red wig. "I'm Mimic."

Of course. Lorna and Anna were both organisers of PonyCon, which started as an internet forum for collectors and is now an annual event. Several hundred people turned up at Brunel University in Middlesex to admire each other's toys, swap and sell and celebrate their favourites.

And dress up. Some had complete costumes, including horse heads, others were simpler: there was even what looked like a man on stage, wearing a long blonde wig. Could it be? Hadn't they mostly been banished to the Man Creche in the next room, with its sports magazines?

No, it really was a man. Dennis from the Ukraine. The husband of Lorna. When they first met, she wasn't into all this. "I lulled him into a false sense of security," she said. And now? "Now we are worshipping the pink crack!" Sorry? She couldn't repeat that; she was up on stage with her partner, who had a dazed grin. Like one of those people who have been hypnotised and are about to eat an onion, thinking it's an apple.

"Dennis is dressed as Sports Time," said the Mistress of Ceremonies. "A very enthusiastic pony. Give us a twirl!" Dennis did, a nightmare beauty queen. "Dennis," says the commentator, "likes to drink."

The room cheered, with a predominantly female voice. Most people there were women in their late twenties and early thirties. Just the right age to have been pony fodder when Hasbro launched its plastic toys in 1982. A bewildering variety was produced, from the original Earth Ponies to the fairy-like Breezies, so girls would become hooked on collecting.

The stable door was bolted in 1985, but five years ago Hasbro relaunched My Little Pony. Presumably it had worked out that little girls grow into women with money in their pockets, who have children of their own. Or who just want another play.

"It makes you feel like a kid again," said Anna Britton, aka Sky Dancer, who won the fancy dress competition. A couple of tiny girls drew oohs and aahs, but they were never going to beat the determined young women who had stitched their own wings. "It really does take you back to childhood ... well, I don't really play with them, like making voices and everything." No? "No. But I know people who do."

She has a stressful job, working all day in a laboratory, doing things like "putting metals in acid, using chemicals that are really quite deadly". Then she goes home. "I stroke the hair of a pony and it all just fades away. You go to a place where there are no worries, no responsibilities."

She is a scientist. Lorna Dounaeva works for the Government. Others at PonyCon were in law, business or money. So many of these people doing maniacally daft things had important or pressured jobs.

And lots of ponies. Anna had 50 as a child, but put them away in the attic until five years ago, when she heard they might be worth something and sold them. "I regretted it straight away. It has taken until now to buy back the same kind of ponies I played with. I've picked up a few more on the way."

Another 750 actually. None of them worth as much as the Holy Grail of My Little Pony hunting, a Greek one in an Easter egg that sold for £1,000 on eBay last year. Anna's latest three had cost a fiver each. "There's Kingsley the Lion." He was pink. And not a pony. This was some strange subset. "There's Creamsical the giraffe." Yellow. "Yes. There's this one." He's blue. "Spunky the camel."

Did Anna, erm, have a boyfriend? "Oh yes. He knew about this before we got together. He doesn't mind." Did he have any obsessions? "No. He's doing a PhD in plant metabolism."

Hasbro supports PonyCon, giving a limited-edition pony to those who attend. A fortnight ago it held a charity auction in New York, selling off ponies decorated by stars, including Courteney Cox. Last year's UK PonyCon raised £5,000 for charity by auctioning animals signed by Bill Bailey, among others.

But it goes way beyond celebs. Yesterday, enthusiasts with furrowed brows examined ponies that had been customised, some by people with a delightfully sick sense of humour: like the row of pastel creatures hanging from a pony gallows, each with a noose around its neck.

Lorna collects politicians. She takes a pony to work in Westminster every day in case she sees someone in the street who might sign it. "Not in the office, though. I want to keep my work and private life separate." Quite wise. "I do tell people what I do, but they can't quite take it in."

She has got a David Cameron and a William Hague, but her prize exhibit yesterday had an almost illegible name scrawled on its rear. "A friend in the States pushed her way through the crowd." It was John McCain.

Lorna keeps her 300 ponies in a special cupboard, all boxed up, she said. "I want them to look like they did when I was a child and I first unwrapped the present and went 'Wow!'"

She has no children of her own, yet. If she does, will they be allowed to open the boxes? "No. They'll have to get their own ponies. They're not playing with mine."

Pony express: A winner from the Hasbro stable

* Launched by Hasbro in 1982, My Little Pony became a popular toy with young girls, even outselling Barbie dolls for a brief time in the 1980s.

* The first generation comprised six characters, named collectively as the Earth Ponies.

* A vast array of varieties, including Sea Ponies, Flutter Ponies and Mermaid Ponies soon joined the Earth Ponies.

* My Little Pony appeared on television for the first time in 1984 and a regular series followed in 1986, as did the feature film 'My Little Pony: The Movie'.

* It has spawned hundreds of websites for collectors, and some, such as Baby Birthday Ponies, are valuable and can fetch up to £90.

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